<h2>DESCRIPTION</h2>

<em>i.landsat.acca</em> implements the <b>Automated Cloud-Cover
Assessment</b> (ACCA) Algorithm from Irish (2000) with the constant
values for pass filter one from Irish et al. (2006). To do this, it
needs Landsat band numbers 2, 3, 4, 5, and 6 (or band 61 for Landsat-7
ETM+) which have already been processed from DN into reflectance and
band-6 temperature
with <em><a href="i.landsat.toar.html">i.landsat.toar</a></em>).

<p>The ACCA algorithm gives good results over most of the planet with the
exception of ice sheets because ACCA operates on the premise that
clouds are colder than the land surface they cover. The algorithm was
designed for Landsat-7 ETM+ but because reflectance is used it is also
useful for Landsat-4/5 TM.

<h2>NOTES</h2>

<em>i.landsat.acca</em> works in the current region settings.

<h2>EXAMPLES</h2>

Run the standard ACCA algorithm with filling of small cloud holes
(the <b>-f</b> flag): With per-band reflectance raster maps
named <tt>226_62.toar.1, 226_62.toar.2, </tt> [...] and LANDSAT-7
thermal band <tt>226_62.toar.61</tt>, outputting to a new raster map
named <tt>226_62.acca</tt>:

<div class="code"><pre>
i.landsat.toar sensor=7 gain=HHHLHLHHL date=2003-04-07 \
  product_date=2008-11-27 band_prefix=226_62 solar_elevation=49.51654

i.landsat.acca -f band_prefix=226_62.toar output=226_62.acca
</pre></div>


<h2>REFERENCES</h2>

<ol>
  <li>Irish R.R., Barker J.L., Goward S.N., and Arvidson T., 2006.
    Characterization of the Landsat-7 ETM+ Automated Cloud-Cover
    Assessment (ACCA) Algorithm. Photogrammetric Engineering and Remote
    Sensing vol. 72(10): 1179-1188.</li>
  
  <li>Irish, R.R., 2000. Landsat 7 Automatic Cloud Cover Assessment. In
    S.S. Shen and M.R. Descour (Eds.): Algorithms for Multispectral,
    Hyperspectral, and Ultraspectral Imagery VI. Proceedings of SPIE,
    4049: 348-355.</li>
</ol>

<h2>SEE ALSO</h2>

<em>
<a href="i.atcorr.html">i.atcorr</a>,
<a href="i.landsat.toar.html">i.landsat.toar</a>
</em>

<h2>AUTHOR</h2>

E. Jorge Tizado  (ej.tizado unileon es), Dept. Biodiversity and Environmental Management, University of Le&oacute;n, Spain

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